Nearly half of the world's 634 types of primates are in danger of becoming extinct because of human activity, according to a scientific review presented today.

Scientists meeting at the International Primatological Society Congress in Edinburgh, Scotland, a six-day conference that opened Sunday, hope the report - which counts species and subspecies of primates across the world - will help spur global action to defend mankind's nearest relatives from deforestation and hunting.

In the most comprehensive review of the world's apes, monkeys, and lemurs in 12 years, primatologists warned that species from the giant mountain gorillas of central Africa to the tiny mouse lemurs of Madagascar are on the "Red List" for threatened species maintained by the International Union for Conservation of Nature, or IUCN.

The review was funded by Conservation International, the Margot Marsh Biodiversity Foundation, Disney's Animal Kingdom and the IUCN.

It is part of an examination of the state of the world's mammals due to be released at the 4th IUCN World Conservation Congress in Barcelona, Spain, in October.

Terrifying threat

In Asia, more than 70 per cent of primates are classified as vulnerable, endangered or critically endangered - meaning they could disappear soon.

"What is happening in South-east Asia is terrifying," said Jean-Christophe Vie, deputy chief of the IUCN Species Program.

"To have a group of animals under such a high level of threat is, quite frankly, unlike anything we have recorded among any other group of species to date."

In Africa, 11 of the 13 kinds of Red Colobus monkey assessed were listed as critically endangered or endangered.

Some types of the small rust-coloured monkey have not been seen in 25 or 30 years.

'Act now'

"It is not too late for our close cousins the primates, and what we have now is a challenge to turn this around," said Russell Mittermeier, president of Conservation International and the chairman of the IUCN Species Survival Commission's primate specialist group.

"The review paints a bleak picture. Some primates are quite literally being eaten to extinction.

"But it is by no means a doomsday scenario.

"There is a lot of will here among these scientists in Edinburgh and in the countries where primates live."

Mittermeier pointed to recent successes in turning around populations such as the Black Lion Tamarin (Leontopithecus chrysopygus) in Brazil, which was downgraded to endangered from critically endangered in 2003 thanks to three decades of conservation efforts.

The review also noted the discovery, since 2000, of 53 species of primates previously unknown to science - 40 from Madagascar, two from Africa, three from Asia and eight from Central and South America.